Self-leveling camera head

ABSTRACT

A self-leveling camera head includes an eccentric leveling weight assembly that is supported inside an outer housing for free rotation about an axis. The leveling weight assembly can be removably coupled to a separate camera module assembly supported inside the outer housing for rotation about the axis so that its images will be “upright”, i.e. earth normal. A slip ring assembly includes a fixedly mounted connector assembly that removably mates with a contact assembly mounted to the camera module assembly. In an alternative embodiment the camera module assembly does not rotate within the outer housing. Instead a processing circuit processes a video output from a high resolution image sensing device in the camera module assembly, generates a sub-sampled region and rotates it into a predetermined orientation for display. The output of an orientation sensor in the camera head may be processed to achieve the predetermined desired orientation of the video that is stored or displayed.

FIELD OF THE INVENTION

The present invention relates to optical viewing systems, and moreparticular, to video pipe inspection systems.

BACKGROUND OF THE INVENTION

There are many applications where a video camera may be used, where thetarget being observed is not oriented such that it is “upright”, i.e.earth normal, in the video scene that is being presented on a monitoringor recording device. Such is often the case in video inspection systems,where a camera is used to look inside of an opening, and the camera mayrotate during its traversal towards the observation point. It is alsothe case where a fixed orientation camera is used to observe variableorientation objects—such as a camera observing a manufacturing processthat produces items with variable orientation (such as text printed onbottle caps, which are affixed to bottles, and are being monitored asthey roll by). It is further often desirable to orient the video so thatit more closely approximates “upright” and normal viewing conditions.This can help to visually orient the viewer, and can help prevent neckstrain from having to cock the head to the side to bring the imagecloser to normal.

Video pipe inspection systems are commonly used to inspect sewer, waterand well pipes for blockages and defects. Electrical conduits and otherlong narrow passages may be similarly inspected. Typically a resilientflexible push cable is pushed down the pipe. A rugged camera headconnected to the distal or remote end of the push cable receives powerthrough the push cable. A video signal from an internally mounted videocamera sends NTSC or other video signals back through the push cable fordisplay and recording. The camera head is usually centered inside thepipe by radially extending brushes or fins. Alternatively, the camerahead may be supported by small wheels that roll along the interior ofthe pipe. See for example U.S. Pat. No. 6,545,704 B1 of Mark S. Olssonet al. assigned to Deep Sea Power & Light Company of San Diego, Calif.

As the camera head snakes its way through the pipe it usually rotates asthe push cable twists and turns. The video image follows this motion.Users would prefer a video image that maintains its frame of referenceso that the location and nature of defects can be more easilyrecognized. However, since the camera head is inaccessible after it hasbeen pushed down the pipe, it cannot be manually righted. In some cases,water may be present in the bottom of the pipe, in which case the viewerhas a frame of reference, but even then, the periodic twisting of thevideo image as the camera head moves along the pipe can be very tediousand annoying. Furthermore, water is not always present, or it may fillthe pipe entirely. In either of these cases, there is no frame ofreference to tell the viewer which part is the top of the pipe.

U.S. Pat. No. 4,372,658 of O'Connor et al. discloses a pipe inspectionapparatus in which a camera is supported for rotation by ball bearingsmounted within a wheeled housing and a weight is used to orient thecamera. Slip rings are also provided within the housing for transmissionof electrical control signals to the camera. This design is not compactand rugged enough for use by plumbers.

UK patent application GB 2 342 419 A filed in the name of PearpointLimited on Oct. 5, 1998 and published Apr. 12, 2000 discloses a camerahead for pipe inspection in which forward looking and sideways lookingcameras are mounted within a rotatable member suspended between bearingsat opposite ends of a casing. A motor rotates the member to compensatefor motion in the forward looking view. An operator controls the viewobtained from the camera head with a keypad and joystick which providesthe control signals to the camera head. A commercial version of thiscamera head incorporates “auto uprighting” of the cameras. The Pearpointcamera head is complex, expensive to manufacture and subject to failuressince it lacks the ruggedness required in many pipe inspectionapplications. The motorized mechanisms take up substantial space insidethe camera head, thereby making it difficult to downsize the camera headfor inspecting small pipes. Power and control signals must be sent tothe motor, requiring extra conductors in the push cable.

U.S. Pat. No. 6,611,661 of Buck discloses a camera head for pipeinspection in which the camera body is mounted for free rotation withina camera housing and a leveling weight made of tungsten or lead isphysically attached to the camera body in a permanent fashion. Thecenter of mass of the weight is displaced from the axis of rotation ofthe camera body so that the camera body is leveled via gravitationalforces. A bearing is positioned between the camera body and the camerahousing. A slip ring has portions that fit on inner and outer races ofthe bearing. However, this design does not lend itself to easy removaland/or repair of the video camera and associated electronics within thecamera head.

In the past, there have also been electronic solutions to the problem oforienting a video image from a remote video camera. If one is onlyinterested in a rotation of one hundred and eighty degrees (the coarsestrotation—commonly called a screen flip), this can easily be done in oneof two ways. The video transmitted by the camera can be converted it toa digital format and re-mapped so that it is presented with what wasoriginally the lower, right most pixel, remapped to the upper left mostcorner, and so on. The remapped digital data can then be reconverted toanalog form. Alternatively in the case of a monitor having a cathode raytube, the vertical and horizontal gun polarity can be reversed. Insteadof scanning from left to right, top to bottom, the guns scan right toleft, bottom to top. Either approach yields the same effect of rotatingthe video from the camera by one hundred and eighty degrees.

A digital flip and/or mirror is also commonly used both in LCD monitorsas well as in some CCD cameras. One advantage of doing the flip beforerecording is that the corrected image is then recorded. Pipe inspectionsystems in use today that invert the image on the monitor do not allowthe inverted image to be recorded. The main advantages of the flipapproach are low cost and the fact that it preserves the original aspectratio of the video (typically 4:3). The primary disadvantage is thelimited rotational resolution (only offering two positions—0 degrees and180 degrees of rotation).

Some manufacturers of video equipment have taken a video stream,converted it into a digital format, performed a matrix operation on thedigital data to rotate the entire image by a predetermined amount, andthen re-converted the digital date to an analog signal. This approach isoptimal in terms of the rotational resolution, however it is extremelycomputationally intense, and therefore requires a significant cost inparts and power. It also suffers from the drawback that the rectangular4:3 array is clipped so that some video content is lost at any anglesother than zero and one hundred and eighty degrees. At rotations ofninety and two hundred and seventy degrees, the entire right and leftlobes of the source video are lost.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention a self-levelingcamera head includes an outer housing and a camera module assemblyincluding an image sensor supported inside the outer housing for freerotation around a first axis. A leveling weight assembly is supportedinside the outer housing separate from the camera module assembly forfree rotation about a second axis, which preferably substantiallyconincides with the first axis, as a result of a center of gravity ofthe leveling weight assembly being displaced from the second axis. Theleveling weight assembly is removably coupled to the camera moduleassembly so that the leveling weight assembly can turn the camera moduleassembly to a predetermined angular orientation.

In accordance with another aspect of the present invention a camera headincludes an outer housing and a camera module assembly including animage sensor supported inside the outer housing for free rotation aroundan axis. A slip ring assembly includes a connector assembly thatremovably mates with a contact assembly. The contact assembly is mountedto the camera module assembly for rotation therewith, and the connectorassembly is fixedly mounted within the outer housing.

In accordance with yet another aspect of the present invention a camerahead includes an outer housing and a camera module assembly including animage sensor supported inside the outer housing for free rotation aroundan axis. A slip ring assembly includes a first portion mounted to thecamera module for rotation therewith and a second portion fixedlymounted within the outer housing. The second portion can be plugged intothe first portion along the axis.

The slip ring assembly can be unplugged to allow for repair orreplacement of the camera module assembly.

In accordance with still another aspect of the present invention a videopipe inspection system has a camera head including a high resolutionimage sensing device. A push cable is connected to the camera head. Aprocessing circuit connected to the push cable processes a video signalfrom the camera head to generate a sub-sampled region and rotates thesub-sampled region into a predetermined orientation for display.

In accordance with still another aspect of the present invention a videopipe inspection system includes a camera head having an image sensingdevice and a push cable connected to the camera head. An orientationsensor senses an angular orientation of the camera head. A processingcircuit is connected to the push cable for processing a video signalfrom the camera head and an output signal from the orientation sensor sothat images that are stored or displayed have a predeterminedorientation.

In accordance with another aspect of the present invention a camera headincludes a rear housing assembly with a female threaded forward end andan illumination window. The camera head further includes an illuminationwindow retainer having a forward end for holding the illumination windowand a female threaded rearward end. A male threaded coupling ring isprovided for having the rear housing assembly screwed over a rearportion of the coupling ring and the illumination window retainerscrewed over a forward portion of the coupling ring. A camera moduleassembly is supported inside the enclosure defined by the joining of therear housing assembly, illumination window, illumination window retainerand coupling ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled sectional view of an embodiment of aself-leveling camera head in accordance with our invention taken alonglines 1-1 of FIGS. 2A, 2B and 2C.

FIGS. 2A, 2B and 2C collectively form a reduced exploded isometric viewof a the self-leveling camera head illustrated in assembled andsectioned form in FIG. 1.

FIG. 3 is an exploded isometric view of the connector assembly of theslip ring assembly of the self-leveling camera head of FIG. 1.

FIG. 4 is an enlarged sectional view of the connector assembly takenalong lines 4-4 of FIG. 3.

FIG. 5 is an exploded isometric view of the micro slip ring rotatingcan, coupling ring and LED window of the self-leveling camera head ofFIG. 1 illustrating further details thereof.

FIG. 6 is an isometric view of the rear housing assembly, ball bearingsupport, micro slip wire base, micro slip ring rotating can, couplingring, and LED window of the self-leveling camera head of FIG. 1,illustrating further details thereof.

FIG. 7 is an exploded, part elevation, part sectional view of theself-leveling camera head of FIG. 1 illustrating further detailsthereof.

FIG. 8 is an exploded, part sectional, isometric view of theself-leveling camera head of FIG. 1 illustrating further detailsthereof.

FIG. 9 is a part sectional, part side elevation view of the assembledself-leveling camera head of FIG. 1 illustrating further detailsthereof.

FIG. 10 is an isometric view similar to FIG. 9.

FIG. 11 is an enlarged cross-sectional view of the self-leveling camerahead of FIG. 1 taken along lines 11-11 of FIG. 1 illustrating details ofits contact assembly.

FIG. 12 is a block diagram of a video pipe inspection system thatre-orients video images electronically.

FIGS. 13-19 are a series of diagrammatic images of video displaysillustrating the manner in which the video pipe inspection system ofFIG. 12 electronically re-orients the video images.

DETAILED DESCRIPTION

Referring to FIG. 1, a self-leveling camera head 10 includes a stainlesssteel generally cylindrical outer housing 12 having a central axis 14(FIGS. 2A, 2B and 2C). A camera module assembly 16 (FIG. 2B) includingan image sensor 18 is supported inside the outer housing 12 for freerotation around the central axis 14 via Teflon (trademark) or Tefloncomposite split-ring bushing 20. Other forms of low friction materialmay be used to fabricate the bushing 20. The image sensor 18 ispreferably a charge coupled device (CCD) and has associated filterelements for producing output signals that represent a color image basedon light reflected from scenes and objects within a field of viewestablished by a lens assembly 22 illuminated by an LED assembly 24(FIG. 2B). The image sensor 18 could also be a CMOS imager.

The lens assembly 22 (FIGS. 1 and 2B) focuses light on the image sensor18. It is mounted in a threaded assembly so that it can be screwed backand forth along the central axis 14 during factory calibration to ensurethat the light is focused in an optimum manner on the image sensor 18.Various O-rings (visible but unnumbered in FIG. 1) ensure that waterdoes not pass into the lens assembly 22.

A leveling weight assembly 26 (FIG. 2C) is supported inside the outerhousing 12 separate from the camera module assembly 16 for free rotationabout the central axis 14 as a result of a center of gravity of theleveling weight assembly 26 being displaced from the central axis 14.Means are provided for enabling removable coupling of the levelingweight assembly 26 and the camera module assembly 16 so that theleveling weight assembly 26 can turn the camera module assembly 16 to apredetermined angular orientation as the camera head 10 rotates duringinsertion into a pipe P (FIG. 12). In the illustrated embodiment, theremovable coupling means comprises a key including mating portions ofthe leveling weight assembly 26 (FIG. 2C) and the camera module assembly16 (FIG. 2B). These mating portions include a part cylindricalprojecting portion 28 (FIGS. 1 and 6-8) on the rear side of the cameramodule assembly 16 that fits within a similarly shaped opening 30 (FIGS.2C and 6) in the leveling weight assembly 26.

The lower half-cylinder portion 26 a of the leveling weight assembly 26provides an eccentrically located weight. The leveling weight assembly26 is preferably made of Tungsten which makes the leveling weightassembly 26 relatively heavy for its size. The remainder 26 b of theleveling weight assembly 26 extends around the periphery of the opening30. Together the portions 26 a and 26 b provide a round outer peripheralsurface. A ball bearing assembly is used to support the leveling weightassembly 26 for free rotation about the central axis 14. One race of theball bearing assembly is provided by the round outer peripheral surfaceof the portions 26 a and 26 b on which a plurality of ball bearings 32(FIG. 1) roll. A ball bearing support 34 (FIG. 2C) captures the ballbearings 32 in individual curved recesses 34 a on one side and holdsthem in place against a circular flange 26 c (FIGS. 1 and 2C) thatextends radially from the leveling weight assembly 26. Another race ofthe ball bearing assembly is provided by the inner surface of the outerhousing 12. A snap ring 35 is positioned in a groove formed in theinside wall of the outer housing 12 and is used to hold the levelingweight assembly 26 in place inside the outer housing 12 when the cameramodule assembly 16 and its supporting structure (hereafter described)are removed from the forward part of the outer housing 12 during serviceor assembly.

A slip ring assembly extends through the leveling weight assembly 26 andremovably connects to the camera module assembly 16. The slip ringassembly is separable into two portions to allow the camera moduleassembly 16 to be removed from the forward end of the outer housing 12.This allows the camera module assembly 16 and its associated electronicsmounted on circuit board assemblies 36, 38 and 40 (FIG. 1) to be easilyrepaired and/or replaced. The slip ring assembly includes a contactassembly 42 (FIGS. 2B and 11). A connector assembly 44 (FIGS. 3, 4, 9and 10) plugs into the contact assembly 42. The contact assembly 42includes a plurality of resilient, flexible, straight conductive contactbrushes 46 (FIGS. 2B and 11) having proximal ends soldered to circuitboard assemblies 48 and 50 (FIG. 11).

The outer housing 12 includes an outer cylindrical rear housing assembly52 (FIG. 2C), a forward LED (illumination) window 54 (FIG. 2A) made ofacrylic, Nylon (trademark), polycarbonate or other hard transparentplastic material, and a coupling ring 56. An LED (illumination) windowretainer 58 (FIGS. 2A and 5) mates with the coupling ring 56 to retainthe LED window 54. The forward end of the LED window retainer 58 has aradially inwardly projecting portion which holds onto a rear shoulder ofthe LED window 54. In the embodiment illustrated, the coupling ring 56has male threads formed on its exterior as best seen in FIG. 1. Theforward end of the rear housing assembly 52 has female threads formed onits interior so that it can be screwed over the rear portion of thecoupling ring 56. Similarly, the rear portion of the LED window retainer58 has female threads formed on its interior so that it can be screwedover the forward portion of the coupling ring 56. The camera moduleassembly 16 is thus supported inside the enclosure defined by thejoining of the rear housing assembly 52, LED window 54, LED windowretainer 58 and coupling ring 56. The coupling ring 56 extends forwardof the camera module assembly 16. An O-ring 57 is seated in a grooveformed in the coupling ring 56 between the rear portion of its malethreads and the forward portion of its male threads and provides a rearwatertight seal. Another O-ring 59 provides a forward watertight sealbetween the LED window 54, LED window retainer 58 and coupling ring 56.The construction of the outer shell of the camera head 10 allows foreasy disassembly for repair and provides a large clearance frontalopening away from the attachment of the push cable for installation andremoval of the leveling weight assembly 26 and the camera moduleassembly 16.

A window 60 (FIG. 1) made of a high strength scratch resistant materialsuch as Sapphire is mounted front of the lens assembly 22 in a centralaperture in the LED window 54 with O-ring 62 and retainer rings 64 and66. The window 60 is fixed in place using a tube whose reward flared endis held by a retaining washer 68.

The connector assembly 44 (FIGS. 3 and 4) includes a micro connectorplate assembly 70 with male plugs 70 a, 70 b, 70 c and 70 d (FIG. 6),micro connector circuit board 72, and micro ring base 74 which areassembled along the central axis 14. The large ends of male plugs 70 a,70 b and 70 c mate with female connectors (not illustrated) in acoupling that screws over the rear end 96 of the outer housing 12 inorder to transmit electrical signals. The male plug 70 d provides amechanical alignment mechanism. The slip ring assembly may provide an RFconnection path via two of the three male plugs 70 a, 70 b and 70 c ofthe connector assembly 44.

Micro silver graphite rings 76, 78 and 80 (FIGS. 3 and 4) are separatedby insulating micro ring spacers 82 and 84 (FIG. 3) and are all heldover a rectangular post 86 of the micro ring base 74 by a micro ring cap88. Three female pin receptacles 90 are positioned in correspondingholes in the micro connector circuit board 72 and micro ring base 74.The pin receptacles 90 receive the forward ends of the male plugs 70 a,70 b and 70 c. A slotted round head screw 92 screws through a hole inthe post 86 and into the micro ring cap 88. An O-ring 94 (FIG. 3) standsoff the head of the screw 92 from the micro connector plate assembly 70.The micro plate assembly 70 is captured in a cylindrical recess formedin the rear end 96 (FIGS. 1 and 2C) of the rear housing assembly 52 viasnap ring 98. O-rings 100 and 102 (FIG. 2C) provide water tight sealsthat prevent liquid in the pipe being inspected from entering the outerhousing 12 past the micro connector plate assembly 70. The silvergraphite rings 76, 78 and 80 are connected via terminals and wires (notillustrated) to the micro connector circuit board 72 (FIG. 3) and thepin receptacles 90.

A cylindrical micro slip ring rotating can 104 (FIGS. 1, 2B, 6 and 7)surrounds and supports the camera module assembly 16 and rotatablyslides against the Telfon split-ring bushing 20 at its forward end. Themicro slip ring rotating can 104 also carries the lens assembly 22 andthe LED assembly 24. The projecting portion 28 (FIG. 7) on the rear sideof the camera module assembly 16 includes a micro slip wire base 106(FIGS. 2B, 6, 7 and 8) and a micro slip wire cap 108 secured togetherwith screws 109 (FIG. 2B). The projecting portion 28 conformably fitswithin the opening 30 in the leveling weight assembly 26. Thus, duringassembly of camera head 10 the connector assembly 44 (FIGS. 3 and 4)plugs into the contact assembly 42 (FIGS. 2B and 11) through theleveling weight assembly 26. The connector assembly 44 and the contactassembly 42 axially mate, i.e. they plug and unplug via relativelongitudinal movement along the central axis 14. In addition, at thesame time, the leveling weight assembly 26 is coupled to the projectingportion 28 attached to the rear end of the camera module assembly 16 andsurrounded by the rotatably supported micro slip ring rotating can 104.A very important advantage of the structure of our camera head 10 isthat the connector assembly 44 can be removed from the rear end 96(FIG. 1) of the rear housing assembly 52 by removing snap ring 98. Thiscan be accomplished without having to remove the leveling weightassembly 26 or the camera module assembly 16. A significant advantage ofthe configuration of the camera head 10 lies in the fact that its slipring assembly is modular and is not integrated into or connected to theouter housing 12. This allows its two portions, namely, the contactassembly 42 and the connector assembly 44, to be unplugged andseparately removed for ease of service.

The cylindrical micro slip ring rotating can 104 (FIGS. 1 and 2B) canfreely rotate against Teflon split-ring bushing 20 about the centralaxis 14 and the leveling weight assembly 26 can freely rotate againstthe ball bearings 32 (FIG. 1) about the central axis 14. This allows theleveling weight assembly 26 to turn the camera module assembly 16 underthe force of gravity to a predetermined angular orientation, preferablyso that the images generated with the output of the image sensor 18 willbe upright on a CRT or other display device. The micro slip wire base106 (FIG. 6) is screwed into a micro slip wire base ring 110 (FIG. 2B).The micro slip wire base ring 110 is retained in the slip ring rotatingcan 104 by a spring wire 111. When assembled, all of the componentsillustrated in FIG. 2B spin together about the central axis 14.

The circuit board assemblies 48 and 50 (FIGS. 2B and 11) are mounted inspaced apart opposing relationship inside the micro slip wire base 106,behind the micro slip wire cap 108. Each of the circuit board assemblies48 and 50 supports the proximal or inner ends of three of the straight,resilient contact brushes 46, the intermediate portions of which rideagainst corresponding ones of the micro silver graphite rings 76, 78 and80 as best seen in FIGS. 9 and 11. The distal or free outer ends 46 a(FIG. 11) of the contact brushes 46 are retained from moving outwardduring installation to maintain contact force on the rings 76, 78 and 80but are allowed to move and slide perpendicularly. As each contact brush46 is bent and loaded against its corresponding ring it shortens andmust be free to move at one end to prevent breakage or damage and tomaintain even and compliant contact force. Spaced apart vertical guidemembers 112 made of suitable insulating dielectric material engage andensure proper alignment of the contact brushes 46. There are a total ofsix contact brushes 46 and they are arranged in three pairs. The contactbrushes 46 of each pair of run on the opposite sides of a correspondingone of the silver graphite contact rings 76, 78 and 80. Use of redundantpairs of opposing contact brushes 46 helps eliminate video noise due toimpacts and vibration. The contact brushes 46 must flex duringinstallation and also during operation, and they are spring-loaded. Thecircuit board assemblies 48 and 50 are identical. Only the proximal endsof the contact brushes 46 are soldered to corresponding ones of thecircuit board assemblies 48 and 50. The guide members 112 hold theintermediate segments of the contact brushes 46 in proper position andalignment. It does not matter which end of each of the contact brushes46 is soldered, however, it is important that the intermediate segmentof each of the contact brushes 46 is free to slide up and down in aguide slot formed in the corresponding one of the guide members 112.This arrangement helps keep the contact brushes 46 from being bent whenthe assemblies 42 and 44 are plugged together.

FIG. 12 illustrates a system 200 for inspecting a subterranean pipe Pwith a camera head 202, electronically re-orienting images of the insideof the pipe, and showing the images on a display 204. The images may berecorded on a VCR 206 or other recording device such as a DVD recorder.A camera module assembly 208 receives power through a video push cable210 and sends video signals through the video push cable 210, The videopush cable 210 may be of the type disclosed in U.S. Pat. No. 5,808,239granted to Mark S. Olsson, the entire disclosure of which is herebyincorporated by reference. In this embodiment, it is not necessary forthe camera module assembly 208 to be rotatable within the outer housingof the camera head 202, thereby eliminating the need for the levelingweight assembly 26 and the slip ring assembly.

The image sensor in the camera module assembly 208 may function withsystems employing EIA, NTSC, CCIR, PAL and other standard analog ordigital video signal formats. A stainless steel coil spring 212surrounds the distal end of the push cable 210 and is coupled betweenthe rear end of the video camera head 202 and a termination assembly214. The coil spring 212 provides the desirable amount of flexibility topermit the video camera head 202 to negotiate tight turns inside of thepipe P. Stainless steel aircraft cables 216 connect the rear of thevideo camera head 202 to the termination assembly 214 to facilitateremoval of the video camera head 202 in case it gets stuck inside thepipe P. In the presently preferred design, only a single aircraft cableis used. Deformable plastic fins 218 are clamped around the coil spring212 to center the camera head 202 inside of the pipe P. Further detailsof the camera head 202 may be found in my co-pending U.S. patentapplication Ser. No. 09/506,181 filed Feb. 27, 2000 of Mark S. Olsson etal., the entire disclosure of which is hereby incorporated by reference.

The push cable 210 (FIG. 12) is wound about a push reel 220 which can berotated to pay out or take in the push cable 210. Further details of thepush reel 220 are disclosed in U.S. Pat. No. 6,545,704 granted Apr. 8,2003 to Mark S. Olsson et al., the entire disclosure of which is herebyincorporated by reference. At the proximal end of the push cable 210 thevideo, power and ground conductors within the push cable 210 are coupledto a slip ring assembly (SRA) 222. Other conductor schemes can beutilized including a two wire system of modulated video on power and aground. The SRA 222 has an integral position encoder, such as thatdisclosed in co-pending U.S. patent application Ser. No. 10/799,473filed Mar. 11, 2004 of Mark S. Olsson et al., the entire disclosure ofwhich is hereby incorporated by reference. The video, power and groundconductors from the SRA 222 are connected to an electronic processingcircuit 224. The video signals from the camera head 202 and the outputsignal from the position encoder within the SRA 222 are processed by theprocessing circuit 224 so that real time video images of the interior ofthe pipe P are shown on the display 204 with overlaid alphanumericdistance, time and/or date information.

Electromagnetic signals are emitted by a flexible transmitter 226 (FIG.12) within the coil spring 212 for detection by a portable hand-heldlocator carried by a person traversing the ground under which the pip Pextends. The locator can determine and display a precise position of thecamera head 202 within the pipe P. An example of such a transmitter isdisclosed in co-pending U.S. patent application Ser. No. 10/061,887filed Jan. 31, 2002 of Mark S. Olsson et al., the entire disclosure ofwhich is hereby incorporated by reference. An example of a suitabletransmitter circuit for driving the transmitter 226 and a suitableportable hand-held locator for detecting the electromagnetic signalsemitted by the transmitter 226 are disclosed in co-pending U.S. patentapplication Ser. No. 10/308,752 filed Dec. 3, 2002 of Mark S. Olsson,the entire disclosure of which is hereby incorporated by reference.

The processing circuit 224 (FIG. 12) can process the incoming sourcevideo in a number of ways to ensure that the images shown on the display204 have the predetermined desired angular orientation as indicated byan orientation sensor 225 such as a two-axis accelerometer. The incomingvideo signal can be converted to a digital format, and then theprocessing circuit 224 can perform a rectangular rotation at ninetydegree increments using the output signal from the orientation sensor225. If the original video (FIG. 13) is rotated to one hundred andeighty degrees (FIG. 14), then remapping as in the case of a screen flipprovides an optimal solution. If the video is rotated to ninety degreesor two hundred and seventy degrees, the video will be on end and can bepresented in one of three ways:

1) The center region can be cropped such that the information that wason the right and left edges of the video source is lost, as illustratedby the cross-hatched regions in FIG. 15. However, the resolution andsquare pixel aspect ratio of the center region (typically the region ofinterest) is maintained. This is similar to matrix rotation at angles ofninety or two hundred and seventy degrees.

2) The video image can be reduced in size so that the horizontaldimension will fit on the display in a vertical orientation, i.e. theentire input image fits at right angles on the screen as illustrated inFIG. 16. This leaves significant “black space” on the right and leftsides of the screen (vertical letter boxing), and lowers the resolutionof the screen image, but maintains the square pixel ratio of the entireimage. The black space is illustrated by cross-hatched regions in FIG.16.

3) The display can be horizontally stretched (as is done commonly with“wide screen” 16:9 format TVs which take a 3:4 aspect ratio signal) asillustrated in FIG. 17. In this case, the original 3:4 signal is rotatedon end, such that it will be in a 4:3 format, and then will behorizontally stretched out to a 3:4 again. This will yield a full screenimage which was significantly distorted in aspect ratio.

Another approach to image reorientation by the processing circuit 224utilizes a high resolution image sensing device in the camera moduleassembly 208. This high resolution image sensing device has a linearresolution in both the vertical and horizontal directions greater thanresolution of the diagonal of the image to be displayed. For instance,if an image sensing device with a 1,000×1,000 element sensor array isused to capture the image, and the display device only needs 640×480pixels, then the 640×480 sub-image (which has a diagonal resolution(square root of sum of squares) of 800 elements) can be rotated withinthe source image to any angle, without loss of resolution or corruptionof aspect ratio. The entire output of the high resolution image sensingdevice is sent to a video processor in the processing circuit 224 thatselects and re-maps the elements within the rotated rectangular clippingregion, and converts them into an analog or digital output format with a3:4 aspect ratio, at full display device resolution as illustrated inFIGS. 18 and 19. This approach has a number of advantages. It allows forrotation to any angle as in the matrix operation above, but does notlose information in the cropping, and thus does not have “letterboxing.It also retains the aspect ratio of the source image as in the screenflip above, but allows for arbitrary rotation. It is also lesscomputationally intense than matrix rotation.

There are further capabilities and advantages of utilizing an“oversized” image sensing device. Motion compensation is possible. Thistype of processing is commonly done with commercially availablecamcorders. It is done by re-mapping the image output rectangle withinan oversized imager, such that the object of interest stays at the samelocation in the output video, even if there is vertical or horizontalmotion in the source. This is done by x and y translation, and norotation is required. With a higher resolution image sensing device itis possible to perform a sub-sampling or over-sampling of the imagesensing device output to yield an electronic zoom in or out without lossof resolution. By changing the position of the output image rectanglewithin the image sensing device, it is possible to perform an electronicpan and tilt by specifying what region of the image sensing device is tobe outputted. The entire oversized source image can be captured at anytime as a high resolution still image and stored and processed at alater time. The video signal comprises a sequence of low resolutionframes, and the processing circuit 224 is capable of selectivelygenerating, automatically at predetermined intervals or upon operatorcommand, one or more high-resolution still images for storage ordisplay.

The diameter of the field of view of the lens assembly, such as 22 (FIG.1), only needs to cover the diagonal of the rotated sub-sampled region.This means that the higher resolution image of the entire frame can be“port-holed”, i.e. vignetted. The camera head 202 may be used forinspection applications, where the orientation of the camera may not be“earth normal.” The camera head 202 can report back its orientation viathe orientation sensor 225 to a video rotation unit in the processingcircuit 224, and the image can be automatically rotated to make theoutput image “normal” (with respect to earth down), without regard tothe orientation of the camera. There are a number of sensor technologiesthat be used within the camera head 202 to facilitate the directionalsensing of earth normal, including but not limited to accelerometers;tilt indicators including hanging mass, conductive ball, bubble(including conductive, thermal, ultrasonic and other); gyroscopes andother inertial systems; and/or single or multi-axis magnetic compassesincluding hall effect, flux gate, GMR, and others. A combination of suchsensors could be used. Further, clues within the video could be used todetermine earth normal-for instance flowing water could be an indicatorof the bottom of scene and therefore earth normal, or objects scatteredon a plane could be assumed to be on the ground, and therefore likelyearth normal.

Thus, the orientation of the camera head 202 with respect to earth couldbe determined either at the camera head via sensors, by the cameramodule assembly 208, by video cues, or by the video processor in theprocessing circuit 224 using video cues. If the camera head 202 makesthe earth normal determination, then it can transmit the informationback to the controller/video processor by means including, but notlimited to, encoding data into the video stream, having a separatecarrier along with the base-band or modulated video which encodes theangle, transmitting the angle on a separate conductor, modulation on thepower line or transmitting the angle information via some other wired orwireless technology. The image could also be rotated in response tooperator commands.

While mechanical and electronic embodiments of our self-leveling camerahead have been described in detail, it should be apparent to thoseskilled in the art that modifications can be made to the same withoutdeparting from the spirit of our invention. For example, instead of aremovable coupling between the leveling weight assembly 26 and thecamera module assembly 16 that relies upon an inter-fitting key, otherforms of coupling means could be employed including, but not limited to,gears, cams, pulleys, screw threads, drive shafts, fluid, or magneticcouplings. As another example, the slip ring assembly could be arrangedso that the silver graphite rings 67, 78 and 80 are mounted to thecamera module assembly 16 and the contact brushes 46 are mounted to theconnector assembly 44. The advantages of one aspect of our invention areachieved by having a slip ring assembly with first and second portionsthat can removably axially plug into one another, with the first portionbeing mounted for rotation with the camera module assembly 16 and thesecond portion fixedly mounted in the outer housing 12. This allows forseparation of the slip ring assembly to permit the camera moduleassembly 16 to be removed from the forward end of the outer housing 12.As still another example, the axis of rotation of the camera moduleassembly 16 and the axis of rotation of the leveling weight assembly 26could be spaced from each other, and one or both of these axes could bespaced from the central axis 14 of the outer housing 12. Other sourcesof illumination besides the LEDs 24 can be utilized such as incandescentlamps. In the embodiment of our camera head illustrated in FIGS. 1-11,the rotational axes of the leveling weight assembly 26 and the cameramodule assembly 16 substantially coincide with one another, and alsosubstantially coincide with the central axis of the outer housing 12 forcompactness and simplicity. However, due to the limitations imposed bymanufacturing tolerances, as a practical matter, the axes of rotation ofthe leveling weight assembly 26, the camera module assembly 16 and thecentral axis 14 of the outer housing 12 cannot be exactly identical. Oursystem for electronically re-orienting the video images is subject to awide variety of modifications not described above. For example, theorientation information from the orientation sensor 224 could be savedand then processed later when the video images were displayed so thatthe images could be properly oriented at that time, instead ofperforming the orientation in real time. Our camera head can not only beconnected to the distal end of a semi-rigid push cable such as the pushcable 210 but may also be towed on the end of a so-called tractor cable.Moreover, the concepts described herein may be utilized in a widevariety of industrial applications not associated with pipe inspectionsuch as assembly line monitoring. Therefore, the protection afforded ourinvention should only be limited in accordance with the scope of thefollowing claims.

What is claimed is:
 1. A self-leveling camera head, comprising: an outerhousing; a camera module assembly including an image sensor supportedinside the housing for free rotation about an axis; a leveling weightcoupled to the camera module assembly; and a slip ring assembly axiallyoverlapping the leveling weight and having first and second portionsconfigured to removably axially plug into one another and to provideelectrical connections between a plurality of fixed connecters mountedto the outer housing and the rotatable camera module assembly, the firstportion of the slip ring assembly including a plurality of flexiblecontact brushes and the second portion of the slip ring assemblyincluding a plurality of rings.
 2. The camera head of claim 1 whereinthe plurality of flexible contact brushes are mounted for rotation withthe camera module assembly.
 3. The camera head of claim 1 wherein theplurality of rings are mounted for rotation with the camera moduleassembly.
 4. The camera head of claim 1 and further wherein the levelingweight is supported within the housing on a bearing assembly.
 5. Thecamera head of claim 1 and further wherein the camera module assembly issupported for rotation in a can that rotates against a bushing.
 6. Thecamera head of claim 1 wherein the first portion of the slip ringassembly extends through the leveling weight.
 7. The camera head ofclaim 1 wherein the leveling weight is physically separate from thecamera module assembly.
 8. The camera head of claim 1 and furthercomprising a removable coupling between the leveling weight and thecamera module assembly.
 9. The camera head of claim 8 wherein theremovable coupling comprises a key including mating portions of theleveling weight and the camera module assembly.
 10. The camera head ofclaim 1 and further comprising a plurality of LEDs mounted to the cameramodule assembly capable of illuminating a field of view of the imagesensor.